The proposed work is a continuation of our general effort toward an understanding of structure-function relations in biological membranes. Several projects are under way. We are examining the structure and function of the Ca ions, Mg ions ATPase complex in E. coli in order to define the polypeptide composition and the function of each polypeptide in the complex. We are examining a reconstituted sugar transport system. The isolated proteins for lactose transport in S. aure us have been incorporated into lipid vesicles. We are attempting to examine the transport capacity of these vesicles. Our studies with a unique fluorescent probe, parinaric acid, are being extended to the examination of animal cell membranes.